This application is based upon and claims the benefit of priority of Japanese Patent Application No. 2000-213086 filed on Jul. 13, 2000, the content of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a resin shield circuit device.
2. Description of Related Art
Conventionally, a resin shield circuit device is formed by accommodating a circuit board (a printed wiring board), on which circuit elements are mounted and which has connecting terminals leading to outside, into a recess of a resin case and, after pouring liquid resin from an opening of the recess into inside of the recess by potting, hardening the liquid resin. This is hereinafter called a potting type resin shield circuit device.
Further, a conventional resin mold semiconductor device is formed by bonding semiconductor chips on metal bases stamped together with lead frames, connecting respective wiring metal regions of the semiconductor chips to the respective lead frames by wire bonding or in use of balls or pumps, then, shielding the connecting portions and the semiconductor chips by resin molding and, finally, cutting off junctions connecting the respective lead frames. This is hereinafter called molding type resin shield circuit device.
Furthermore, a conventional resin connector has a connecting terminal protruding into a recess of a connector body for coupling with an opponent plug. A base of the connecting terminal is fixed to the connector body by insert molding. Moreover, a resin shield circuit device, in which the resin connecter mentioned above and the potting type resin shield circuit device are integrated into one body, is also known.
The potting type resin shield circuit device has good characteristics such as exclusion of moisture and improved reliability since the resin filled in the recess of the resin case is exposed to outside only from the opening of the recess, but has problems to solve as described below.
When many of the circuit elements (discrete circuit elements) having lead terminals and many wiring metal pieces are mounted on the printed wiring board, it becomes necessary to cut in advance respective lengths of the lead terminals and connecting portions of the wiring metal pieces to respective predetermined values before inserting the lead terminals and the wiring metal pieces into apertures of the printed wiring board for soldering. Further, it becomes necessary to form wiring patterns on the printed wiring board. Accordingly, manufacturing processes of the circuit device are complicated and much more material is used.
Further, when the circuit element rises for a certain distance out of a flat surface of the printed wiring board, it is necessary that the circuit device has thickness corresponding to at least a sum of length of each of the lead terminals and height of the circuit element. As a result, a more amount of resin for shielding and a larger body of the circuit device are required. Furthermore, in a case of the circuit element having lead terminals that extend in opposite directions from the ends thereof, the lead terminal on a side opposite to the printed wiring board is required to bend by 180 degrees angle. When the circuit element lies on the printed wiring board, the lead terminals are required to bend at approximately right angles so that the manufacturing process is complicated.
Moreover, outside connecting terminals, which connect the wiring patterns of the printed wiring board to outside, protrude out of a resin shield portion. Since heat stress occurs between the outside connecting terminals and the resin shield portion whose heat expansion rates are different, a crack or a small gap, through which moisture is entered into inside of the circuit device, is likely formed at a boundary between contacts of the outside connecting terminals and the resin shield portion, during a long time when the circuit device is used.
An object of the invention is to provide a compact and reliable resin shield circuit device that is manufactured at simpler manufacturing processes and with less amount of material to be used.
To achieve the above objects, in the resin shield circuit device, a resin case is provided with a recess having an opening. Each end of connector terminals is exposed out of the resin case and the other end thereof is embedded into and fixed to the resin case. Base portions of wiring metal pieces are embedded into and fixed to the resin case and connected in circuit with the other ends of the connector terminals. Connecting portions of the wiring metal pieces protrude into the recess. Respective lead terminals of circuit elements are connected and fixed to the respective connecting portions. A resin shield portion filled in the recess covers the circuit elements and the connecting portions of the wiring metal pieces in such a manner that only a flat surface of the resin shield portion is exposed out of the opening of the recess to outside.
According to the resin shield circuit device mentioned above, the resin shield portion is formed generally by potting process and has the flat surface exposed only out of the opening of the recess to outside, resulting in good characteristics of moisture exclusion and reliability, similarly to the conventional potting type resin shield circuit device.
Further, each of the circuit elements is directly mounted on and fixed to each of the wiring metal pieces without using the conventional printed wiring board to be housed in the recess of the resin case so that a volume of the recess is smaller and the manufacturing processes is simpler. It is not necessary to connect a wiring of the printed wiring board to the wiring metal pieces.
Furthermore, since the wiring metal pieces are formed together with the resin case by insert molding, the manufacturing process is simpler.
When the circuit elements are mounted on the printed wiring board, it is very common that main bodies of the circuit elements are positioned at certain distances from a surface of the printed wiring to secure faster flow of potting resin and not to make voids of resin. Accordingly, the amount of resin for shielding of the conventional device is larger, compared with the resin amount of the resin shield portion of the circuit device, in which the lead terminals of the circuit elements are directly fixed to the wiring metal pieces so that idling space in the recess is reduced.
It is preferable that all of the lead terminals are connected inside the resin shield portion to the wiring metal pieces and not exposed out of the flat surface of the resin shield portion. Since the lead terminals of the circuit elements are connected in circuit to outside only through the wiring metal pieces and the connector terminals, there is no risk that moisture enters through gaps between the lead terminals and the resin shield portion that is formed by relatively low density resin, as is the conventional potting type resin shield circuit device. Accordingly, reliability of excluding moisture and hydrolysis due to the moisture is remarkably improved.
Further, preferably, the circuit elements and the wiring metal pieces are arranged not to overlap each other in a direction perpendicular to the flat surface of the resin shield portion. with this arrangement, mounting of the circuit elements on the wiring metal pieces in the recess becomes very easy since the circuit elements can be inserted into the recess and soldered to the wiring metal pieces in a depth direction of the recess without interfering with each other.
Further, it is preferable that the connecting portions extend in the recess in parallel to the flat surface of the resin shield portion. More preferably, the connecting portions extend in the recess on a single hypothetical surface parallel to the flat surface of the resin shield portion. With these constructions, manufacturing processes including setting the wiring metal pieces in an insert molding die and mounting the circuit elements on the wiring metal pieces become simpler and easier.
Furthermore, it is preferable to have a shelf formed integrally with the resin case in a shape of protruding inward out of an inner surface of the recess so that any of the main bodies or lead terminals of the circuit elements is easily mounted on the shelf at a given distance from the flat surface of the resin shield portion.
To secure an adequate positioning of the main body or lead terminal of the circuit element when the circuit element is mounted on the wiring metal piece, it is preferable that the shelf or the connecting portion of the wiring metal piece is provided with a depression.